The unidentified employee was not involved in stunt work but apparently died during preparation for an underwater action scene in Acton, northeast LA county. Filming was not being carried out at the time.

A coroner's spokesperson said on Sunday that the 48-year-old man was pronounced dead at 10am on Friday. It is believed the man suffered a heart attack and then drowned. He had been cleaning a pool that was due to be used in the film, an adaptation of the highly popular radio and TV series of the 1930s, 40s and 50s. It stars The Social Network's Armie Hammer as the masked ex-Texas Ranger who fights injustice in the American old west, with Depp as his native American sidekick, Tonto.

Disney's film, which has Pirates of the Caribbean's Gore Verbinski on board as director, has already had a chequered preproduction. It was shelved in August last year due to spiralling costs before subsequently being revived by the studio a month later with a budget cut from $250m to $215m. The Lone Ranger also stars Helena Bonham Carter and Ruth Wilson in supporting roles. It is due for release in July next year.